from heapq import heappop, heappush


N, M = map(int, input().split())
graph = [[] for _ in range(N)]
pos = {}
for _ in range(M):
    a, b, c, d = map(int, input().split())
    a -= 1; b -= 1
    pos[a, b, c] = len(graph[a])
    pos[b, a, c] = len(graph[b])
    graph[a].append([b, c])
    graph[b].append([a, c])
    
    pos[a, b, d] = len(graph[a])
    pos[b, a, d] = len(graph[b])
    graph[a].append([b, d])
    graph[b].append([a, d])


D = [[-1, None] for _ in range(N+1)]
hq = [(0, 0, None)]
while hq:
    d, node, par = heappop(hq)
    if D[node][0] != -1:
        continue
    D[node] = [d, par]
    for nex, c in graph[node]:
        if D[nex][0] == -1:
            heappush(hq, (D[node][0]+c, nex, node))

INF = 10**10
ans = D[N-1][0]
now = N-1
while now:
    d, par  = D[now]
    c = d - D[par][0]
    i1 = pos[par, now, c]
    i2 = pos[now, par, c]
    graph[par][i1][1] = graph[now][i2][1] = INF
    now = par


D = [[-1, None] for _ in range(N)]
hq = [(0, N-1, None)]
while hq:
    d, node, par = heappop(hq)
    if D[node][0] != -1:
        continue
    D[node] = [d, par]
    for nex, c in graph[node]:
        if D[nex][0] == -1:
            heappush(hq, (D[node][0]+c, nex, node))


print(D[0][0]+ans)